title: Addition of a carbohydrate-binding module enhances cellulase penetration into cellulose substrates.
abstract: BACKGROUND
  Cellulases are of great interest for application in biomass degradation, yet the molecular details of the mode of action of glycoside hydrolases during degradation of insoluble cellulose remain elusive. To further improve these enzymes for application at industrial conditions, it is critical to gain a better understanding of not only the details of the degradation process, but also the function of accessory modules.
  
  
  METHODS
  We fused a carbohydrate-binding module (CBM) from family 2a to two thermophilic endoglucanases. We then applied neutron reflectometry to determine the mechanism of the resulting enhancements.
  
  
  RESULTS
  Catalytic activity of the chimeric enzymes was enhanced up to three fold on insoluble cellulose substrates as compared to wild type. Importantly, we demonstrate that the wild type enzymes affect primarily the surface properties of an amorphous cellulose film, while the chimeras containing a CBM alter the bulk properties of the amorphous film.
  
  
  CONCLUSIONS
  Our findings suggest that the CBM improves the efficiency of these cellulases by enabling digestion within the bulk of the film.
authors.affiliation: Deconstruction Division, Joint BioEnergy Institute, Emeryville, CA 94608, US. dtercek@berkeley.edu.
authors.forename: Vimalier
authors.initials: V
authors.lastname: Reyes-Ortiz
authors.forename: Richard A
authors.initials: RA
authors.lastname: Heins
authors.forename: Gang
authors.initials: G
authors.lastname: Cheng
authors.forename: Edward Y
authors.initials: EY
authors.lastname: Kim
authors.forename: Briana C
authors.initials: BC
authors.lastname: Vernon
authors.forename: Ryan B
authors.initials: RB
authors.lastname: Elandt
authors.forename: Paul D
authors.initials: PD
authors.lastname: Adams
authors.forename: Kenneth L
authors.initials: KL
authors.lastname: Sale
authors.forename: Masood Z
authors.initials: MZ
authors.lastname: Hadi
authors.forename: Blake A
authors.initials: BA
authors.lastname: Simmons
authors.forename: Michael S
authors.initials: MS
authors.lastname: Kent
authors.forename: Danielle
authors.initials: D
authors.lastname: Tullman-Ercek